In endoscopic or laparoscopic surgery, various instruments are inserted through the skin and body wall into a body cavity wherein surgical procedures are to be undertaken. The interior operating site is "visualized" (viewed) using an endoscope or viewing port that also extends into the body cavity. Viewing the cavity interior, a surgeon can conduct operative procedures using different narrow instruments with significantly less trauma than conventional invasive surgery, thus also leading to typically much shorter recovery times for the patient.
To permit better visualization of the internal body cavity, to permit easier access to the operative site, and to reduce the danger of inadvertent engagement with interior organs or tissue, an "insufflation" procedure is first employed. In this procedure a clear fluid, typically carbon dioxide, is injected under pressure into the body cavity to initiate its enlargement and maintain it in the enlarged form.
In order to insufflate, however, a small instrument must be inserted first without visual guidance. After a small incision is made, a thin pneumoperitoneum insufflation needle (called a Veress type needle) or the like is used to puncture the cavity wall and the gas is introduced through the needle. The gas pressure distends the cavity and allows larger implements such as a trocar to enter at a lower risk of injury to internal organs so that the required instrument or instruments can then be inserted. The term "trocar" is sometimes used to refer to a cannula having a cutting edge, and sometimes to a cutting blade within a cannula. It will be employed here in the generic sense. Insufflation needles are comprised of an inner tube with a blunt end and an outer cutting cannula, the inner tube being movable within the outer cannula and spring biased so as to retract into the outer cannula to allow cutting to take place as long as physical resistance is encountered. When penetration is complete, however, the inner cannula extends beyond the cutting edge, exposing a side orifice in the inner cannula through which the gas will flow to create the pneumoperitoneum. A recognized problem in this arrangement is that the inner element retracts into the outer cannula whenever the needle comes in contact with internal vital organs or tissue, thereby exposing the cutting edge and possibly causing further penetration or injury.
In recognition of these problems, various safety devices for laparoscopic instruments have been devised. In U.S. Pat. No. 4,254,762, for example, an endoscope tube is seated within a hollow needle-like trocar and arranged to snap outwardly when the puncture through the body wall has been completed. This is done to enable the trocar and endoscope functions to be combined, so the procedure does not require separate penetrations by a trocar and then an endoscopic instrument. However, "blind" insertion of the insufflation needle is still required, and the danger of inadvertent contact with organs or tissues still remains. Furthermore, the cutting edge of the cannula is still unprotected, because the protruding tip of the endoscope is withdrawn relative to the cutting edge if some resistance is encountered.
In U.S. Pat. No. 5,104,382 a cylindrical hollow element with a cutting end (called an "obturator" in the patent) encompasses an interior rod (called a shield) with a blunt end that is spring loaded in the distal direction. Both the "obturator" and the inner "shield" are within a larger cannula that is also forced through the body wall as the cutting tip penetrates. The blunt end protects temporarily against interior cutting only to the extent of the spring force after the body cavity is reached, and both the "obturator" and "shield" are withdrawn through the cannula at that time.
A different approach is employed in the safety trocar of U.S. Pat. No. 5,116,353, in which a center cutter must encounter resistance, or be withdrawn into the cannula in which it moves. In another patent, U.S. Pat. No. 5,137,509, the surgeon is able to view the relative position of the cylindrical members during penetration, by what is termed an "enhanced visual indicator." Yet another safety puncturing instrument is disclosed in U.S. Pat. No. 4,535,773. In this instrument the point of an implement centrally disposed within a cannula becomes protected by an inner sleeve between the cannula and the implement, which moves out beyond the cutting tip whenever penetration is completed.
The foregoing systems do not provide a satisfactory answer to the problem of enhancing protection for a very small insufflation needle or other device which is to be used during a laparoscopic or endoscopic procedure. Inherently, the insufflation must be undertaken in the "blind" procedure, since insufflation precedes insertion of a viewing instrument. At other times, moreover, it is desired to insert a separate instrument of small diameter, as for purposes of manipulating sutures or other small elements within the body cavity. It is desirable to penetrate such instruments through the body wall and then to employ the instrument immediately, and in a safe fashion. Thus a functional terminal portion on a thin cutting instrument can be very useful, as with an insufflation needle, so that the inserted device can both penetrate into the cavity and be used for some operative function thereafter.